Panel in particular for raised flooring and a process for manufacturing said panel

ABSTRACT

It is disclosed a panel in particular for raised flooring, of the type comprising one concrete layer ( 7 ) having cement ( 8 ), inert material ( 9 ), and additives ( 10   a   , 10   b ) as its components, the panel ( 1 ) comprising a micro-reinforcement made of fibers ( 11 ) resisting to tensile stresses, the inert material ( 9 ) consisting of granules having diversified sizes to limit the presence of gaps between the granules, and the components being compacted together at high pressure to reduce the porosity of the concrete layer ( 7 ).

FIELD OF THE INVENTION

The invention relates to a panel in particular for raised flooring and to the process for manufacturing said panel.

The panel defines the high covering layer of the raised flooring, also called “floating” flooring, that at the lower part thereof has a hollow space for passage of cables and various installations.

Description of the Prior Art

It is known that raised floors are for example widespread in offices, shopping centers, data processing centers, industrial central stations, banks, hospitals, laboratories, and generally in all cases in which passage and switching of many cables is required and several installations are to be routed, such as electric, electronic and telephone installations, data and communication switching equipment and also waterworks, pneumatic installations, gas pipe networks, etc. A raised flooring generally comprises posts or columns of adjustable height that are directly anchored to the raw floor. The upper column ends bear crosspieces that in turn form a support for the covering panels such disposed as to define a continuous plane.

Thus a hollow space is formed between the covering panels and raw floor, along which the above mentioned installations are caused to pass.

These types of flooring are very advantageous because they enable both the different installations to be switched in a precise and efficient manner to the individual users, and a great number of cables and ducts to be conveyed without hindering passage of persons and vehicles, and also because they allow prompt and easy adaptation of the installations to new requirements.

In fact, in order to renovate a given environment, as regards the facilities that can be supplied, it is sufficient to lift the covering panels and redefine the distribution of the installations placed in the hollow space included between the raw floor and the covering panels themselves.

A raised flooring also has the advantage of allowing a quick and simple change of the trampling surface in order to vary the physical features, strength and colors thereof.

Beside the above listed qualities, the mentioned known art also has some important drawbacks.

In fact creation of hollow spaces under the floor with the possibility of lifting the panels and positioning them again in case of renovation or new requirements calls for demanding and expensive functional features to be provided by said raised flooring which features must be much higher than those of the panels or tiles for normal flooring directly resting on the raw floor over the whole extension thereof. Panels in raised flooring are in fact disposed on localized supports and therefore must be able to withstand even important bending efforts. In fact it is possible for a furnishing element or an apparatus to mainly rest on a portion of a panel that is not directly supported.

Panels for raised flooring are then required not to oscillate either in a direction parallel to the trampling surface or in a direction perpendicular thereto and this in spite of the fact that they are substantially devoid of permanent fastening elements, have important thermal expansions, connected with seasonal changes of climate and are subjected to an important wear at their edges when frequent renovations take place.

To meet this requirement a raised flooring has relatively complicated structures that are defined by different elements functionally co-operating with each other. For example, a panel structure is spread that is based on arrangement of substantially three layers.

The first or upper layer, that is the layer in sight, is made of valuable and/or aesthetically agreeable materials, or such arranged as to be adapted to the place where it is used, for example defined by porcelainised grés or antacid resins for chemical laboratories, by rubber for antiskid regions, etc.

The second layer is the one forming the panel thickness and is generally of a cheap material, wood, chipboard, wood and resin mix, concrete filler, calcium sulfate CaSO₄ (gypsum) reinforced with inclusions, etc., for example.

The third layer defines the lower face of the panels and is generally of metal, aluminum or steel for example.

This structure therefore gives the panels the necessary resistance to efforts and also offers a lower resting surface that is smooth and flat.

The composite panels defined by said layers are also associated with peripheral protections or joints or edge elements provided with elastic properties, made of rubber or plastic material for example, so that the same edge elements absorb and compensate for clearances and spaces present between the panels and offer steadiness and noiselessness to the flooring.

Mounting of said different components or layers in fact causes some small size inaccuracies that are compensated for or absorbed by said edge elements. The edge elements provided with elastic properties also have the function of controlling thermal expansions, so that the latter may occur without giving rise to breaking or bending of the panels.

A further quality is represented by the fact that there is a reduction in the wear of the panel edges due to frequent lifting and new positioning of the panels themselves.

Alternatively or in combination with the edge elements, the support crosspieces have protrusions and ribs to be fitted between the panels and allowing the latter to be accommodated in a precise manner and without oscillations.

Therefore, on the whole known panels have a satisfactory functional character but their structure is complicated, heavy, and of high costs and also the production process must make available several components very different from each other.

SUMMARY OF THE INVENTION

Under this situation the technical task underlying the present invention is to obviate the mentioned drawbacks.

Within the scope of this technical task it is an important aim of the invention to devise a panel of simple structure, low cost and high resistance to efforts and wear.

Another aim of the invention is to devise a covering panel that while being of high performance, has reduced thickness and weight.

A further important aim of the invention is to devise a panel that, due to its features and physical properties, ensures a maximum dimensional stability and accuracy in laying.

A still further aim of the invention is to devise a panel that while being manufactured in a substantially standardized manner and based on a reduced number of components homogeneous with respect to each other, can offer a great variety of implementations adapted to the different requirements of use.

The technical task mentioned and the aims specified are achieved by a panel in particular for raised flooring, of the type comprising at least one concrete layer having at least cement, inert material, and additives as its components, said panel comprising a micro-reinforcement made of fibers resisting to tensile stresses, and said inert material consisting of granules having diversified sizes to limit the presence of gaps between said granules and to reduce the porosity of the concrete layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages are pointed out hereinafter by the detailed description of preferred embodiments of the invention, with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic perspective view taken as a whole of a structure known by itself of a raised flooring showing the constituent elements of a covering panel also known by itself in an exploded view;

FIG. 2 is a perspective view of a panel in accordance with the invention taken as a whole and in an isolated position;

FIG. 3 is a diagrammatic elevation side view of a portion of the panel in FIG. 2, including a view in split to highlight the inner components thereof; and

FIG. 4 is a flow chart of the steps to manufacture the panel shown in the FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIGS. 2 to 4, the panel in accordance with the invention is generally identified by reference numeral 1.

It is compared with a panel 2 known by itself shown in an exploded view in FIG. 1 and comprising three layers and edge elements.

In particular the known panel 2 has a first layer 2 a defining the surface features of the panel, a second layer 2 b establishing the panel thickness and made of an inexpensive material having limited strength properties, and a third layer 2 c defining the lower face and made of a metal plate to give the panel the necessary resistance to efforts and also a smooth and flat lower resting surface.

The edge elements are denoted at 2 d and are peripheral protections adapted to absorb and compensate for clearances and spaces present between the panels, to control thermal expansions and also to reduce wear of the panel edges due to frequent lifting and new positioning of same.

The panel bears on a series of crosspieces 3 kept raised by posts or support columns 4 of adjustable height, that are directly anchored to the raw floor 5. Thus a hollow space 6 is formed between the crosspieces 3 and raw floor 5, along which hollow space the cables and ducts of different installations are caused to pass.

Crosspieces 3, columns 4 and generally the whole support structure of the panels do not concern the present invention and can be made in any convenient manner. In accordance with the present invention, panel 1 is of the type comprising at least one concrete layer 7.

The concrete layer 7 has components such as cement 8, inert material 9, solid 10 a and liquid 10 b additives and in addition a micro-reinforcement made of fibers 11 resisting to tensile stresses.

In more detail, fibers 11 are selected from glass yarn, metallic fibers and synthetic fibers of plastic material also variously mixed with each other.

Preferably fibers 11 are a compound including a glass yarn of the alkaline-resistant type (AR) and synthetic fibers of plastic material, namely polypropylene. Also a glass yarn of the alkaline-resistant type (AR), alone, may be used.

This glass yarn has a high content of zirconium oxide ZrO₂, capable of resisting to alkaline attacks. It can be dispersed in the cement or inert material and is structured in the form of continuous filaments of a diameter of twelve-fourteen microns on an average and a length preferably included between three millimeters and twelve millimeters.

Fibers 11 are in an amount included between two and twenty-five percent of the weight of the concrete layer 7, of four percent for example.

A property of these fibers is their tendency to a strong and homogeneous dispersion in a wet or aqueous solution, such as a concrete material being formed, so as to determine an interlacing of threads making a solid and thick micro-reinforcement in the concrete layer 7.

Tendency to dispersion is due to the presence of a binder between the fibers that in an aqueous medium acts like a repellent between the fibers.

It is possible to add to fibers 11 and/or to the inert material 9 a grit 11 a made of glass of the alkaline-resistant type (AR).

This grit may be realized by grinding and than by sifting glass AR, so as to have granules having a size substantially included between two tenths and four tenths of a millimeter.

The inert material 9 advantageously has conveniently selected sizes so as to reduce porosity of the concrete layer 7.

In fact the inert material 9 is of various sizes and comprises granules having diversified sizes complementary with each other.

In this way even the gaps between the granules of bigger sizes are potentially occupied and filled so as to limit and substantially eliminate the porosity of the concrete material.

The minimum porosity also allows to obtain very smooth surfaces, a greater strength and substantially the absence of points of breaking initiation.

In particular, the inert material 9 comprises three aggregates: a big aggregate 9 a including granules having sizes substantially included between ten millimeters and two millimeters, a medium aggregate 9 b including granules having sizes substantially included between one millimeter and half a millimeter and a thin aggregate or filler 9 c including granules having sizes substantially included between five hundredths of a millimeter and one hundredth of a millimeter. Therefore, the medium aggregate 9 b can easily enter the spaces left free by the big aggregate 9 a and the thin aggregate 9 c can enter any region not engaged by the other inert material.

If a grit 11 a is provided, the same can enter the spaces left free by the medium aggregate 9 b, so as to have, in a concrete, granules substantially of four dimensions: big granules of the big aggregate 9 a (10-2 mm), medium granules of the medium aggregate 9 b (1-0,5 mm), granules of the grit 11 a (0,2-0,4 mm), and thin granules of the thin aggregate 9 c (0,05-0,01 mm).

With respect to the overall weight of the concrete layer 7, the big aggregate 9 a is in an amount substantially included between twenty and thirty-five percent, the medium aggregate 9 b is in an amount substantially included between ten and twenty percent, and the thin aggregate 9 c is in an amount substantially included between fifteen and twenty-five percent.

Therefore, the amounts of the different aggregates are substantially similar to each other, although they are not the same.

The amount of the thin aggregate 9 c practically consisting of powder appears to be relatively very high. This amount is in fact similar to the amount of the big aggregate 9 a and similar to or preferably greater than the amount of the medium aggregate 9 b.

As to the amount of the grit 11 a, the same may be substantially equal to the amount of fibers 11.

The inert material 9 is also provided to be formed of elements of high quality each capable of giving satisfactory results when wear and abrasion tests are carried out.

For example, the big aggregate 9 a consists of basalt and/or porphyry and/or quartz; the medium aggregate is sand or the like; and the thin aggregate is a ground material consisting of the same materials forming the other aggregates and /or of siliceous and/or calcareous materials.

The solid 10 a and liquid 10 b additives can be selected from many additives made available by the known art and preferably they are all together in amounts substantially included between one and five percent of the overall weight of the concrete layer 7.

Possibly said additives can be omitted.

Cement 8 is preferably a quick-setting cement.

A feature of the concrete layer 7 is then that of having its components under conditions of great mutual compacting.

The provided compacting is that determined by pressures of at least 500 metric tons (weight) per square meter, equivalent to about 5 million Newton per square meter, or to about 5 Newton per square millimeter, exerted on said components placed in a mould 12.

These pressures can be obtained through appropriate presses used in the ceramic field, for molding clays and the like, for example.

Then to enable formation of the concrete layer 7, the latter obviously has water as the base component, the amounts of which are controlled both as regards the starting mixing of the components and as regards pressing and compacting of same through said presses, and finally as regards drying or curing in an appropriate thermal chamber 13 of the hot air type for example, as better specified in the following.

By way of example, the starting components of a concrete layer being formed can be the following, in percentages on the overall weight: big aggregate: 20% medium aggregate: 10% thin aggregate: 15% cement: 25% water: 25% glass yarn:  4% various additives:  1%

The covering panel 1 for raised flooring preferably comprises, in addition to the concrete layer 7 described above and embodying the load bearing layer, an upper or surface layer 14 defining the face 1 a of panel 1 that is in sight and therefore represents the surface aspect and features of panel 1, as well as the functional character in relation to the environment in which it is inserted.

This upper layer 14 is made of any appropriate material, a ceramic or non ceramic material. For example, the material is selected from ceramic grés, antacid resins, PVC, wood, and an ecological coating including titanium oxide TiO₂.

The upper layer 14 has the feature of being integral in an irremovable manner with the concrete layer 7, in a manner adapted to define a single manufactured article therewith.

Engagement with the concrete layer 7 is obtained through a glue 15 spread on top of the concrete layer 7 or on the base of the upper layer 14 and through subsequent mutual pressing of the two layers.

Pressures for pushing the two layers against each other can be limited and the glue 15 is a binding agent for use with concrete, the adhesive named H40® available from Kerakoll International Rotterdam, for example.

At all events the two layers form a single manufactured article and are sent together for carrying out the finishing operations.

In particular the upper layer 14 and concrete layer 7 jointly define side edges 1 b transverse to the face in sight 1 a and are jointly ground at said side edges 1 b.

The process for manufacturing the said panel in particular for raised flooring is the following.

It is provided that the panel 1 should have a concrete layer 7 in which the components such as cement 8, inert material 9 and various additives are bound to each other through a micro-reinforcement made of fibers resisting to tensile stresses and are compacted with each other at high pressure through a pressing step in a manner adapted to reduce porosity of said concrete material.

In particular said components are bound to each other by fibers 11 that can be of any type and that preferably are made of glass yarn of the alkaline-resistant type or of a compound including a glass yarn of the alkaline-resistant type and synthetic fibers of plastic material.

In the pressing step said components are inserted in a mould and submitted to a pressure of at least 500 metric Tones per square meter (500 T/m²).

As it is well known, a pressure for instance of 1000 T/m² is equivalent to a pressure of 100 kilograms/cm² or to a pressure of 1 kilogram/mm² or to a pressure of 10 Newton/mm².

In addition, it is important to notice that the inert material 9 is selected with granules having diversified sizes in a manner adapted to limit the presence of gaps between said granules and preferably the inert material is selected with three differentiated sizes the amounts by weight of which are similar to each other, the intermediate size being substantially defined by sand.

Also a grit 11 a made of glass of the alkaline-resistant type (AR) and having sizes similar but inferior to said intermediate size may be provided.

The process also involves stages in which the concrete layer 7 is submitted, after pressing, to a step of drying and curing at controlled temperature and humidity.

While the concrete layer 7 may form the whole panel 1, possibly completed with a mere painting, it is preferable for the concrete layer to be engaged in an irremovable manner, by gluing and pressing, with an upper layer 14, so as to form a single article of manufacture.

Engagement may take place either immediately after the pressing operations carried out on the concrete layer 7 and before the latter being dried or cured in the thermal chamber 13 or, when the upper layer consists of ceramic grés, concurrently with a high-pressure pressing operation.

The unitary structure makes it advantageous to carry out a final step in which the concrete layer 7 and upper layer 14 are jointly submitted to a grinding step to define the dimensional features of the panel.

In detail, the preferred manufacturing steps of panel 1 are shown in FIG. 4.

In a first step the inert material 9—with the big aggregate 9 a, medium aggregate 9 b and thin aggregate 9 c —is mixed with cement 8 and these components, in an exactly batched amount to be also obtained by electronic weighing, are inserted in a mixer 16 having a controlled humidity.

Inserted in the same mixer 16 after batching, are possible solid 10 a and/or liquid 10 b additives.

In an auxiliary step the glass yarns or equivalent reinforcing fibers 11 are inserted in mixer 16 as well.

Batching of fibers 11 can take place in two ways.

The first way is by a dry route: fibers 11 are gradually fed into appropriate containers, through Archimedean screws for example, and accurately weighed.

Then the weighed amounts are inserted in mixer 16.

The second way is by liquid route and is identified by chain lines: fibers 11 are inserted in a tank 17 together with a first amount of water 18 a and then the water and fiber solution is batched with a liter-counter and inserted in mixer 16.

The last-mentioned procedure allows also further amounts of solid or liquid additives to be easily inserted in tank 17.

A further amount of water 18 b may be inserted in the tank 17, when a high percentage of water on the overall weight is wished.

If fibers 11 are inserted by dry route, mixer 16 too is substantially dry operated and the humidity necessary to obtain a mixture 19 is drawn from the liquid additives.

The obtained mixture 19 is unloaded, by mere gravimetric filling, into said moulds 12 substantially having the shape of panels 1 to be formed.

Carried out in said moulds 12 is the pressing step denoted at 20 during which the concrete layer being formed is submitted to high pressures, higher than five hundred metric tons per square meter, with extraction of at least part of the excess water and extreme compacting of the components therein present.

This exceptional compacting substantially eliminates the residual porosity of the concrete material.

It is pointed out that the pressing step at 20 may be performed alone, through presses used in the ceramic field, or in combination with a vibration imposed to the moulds 12.

If the moulds 12 vibrate while the concrete layer 7 is submitted to a high pressure, for instance of 3000 or 4000 metric tons per square meter, every residual porosity of the concrete material is eliminated.

Moreover, a vibration applied on the concrete layer 7 gets a very good dispersion of the fibers 11 in the concrete material.

And any excess water is easily eliminated, as water tends to surface the concrete.

It is therefore possible to provide in the starting components of a concrete layer being formed a high quantity of water, for instance reaching a percentage of about 50% of the overall weight.

A high quantity of water is useful to allow a quick filling of the moulds 12, to reduce the process time.

If a high amount of water is foreseen in the starting components, as suggested in 18 b, during the pressing step 20 the high pressure and the vibration may be combined with an aspiration under vacuum of the excess water.

A machine able to vibrate concrete while submitting it to a high pressure, and moreover to aspirate the excess water, is realized by the Company “Longinotti Meccanica” (Florence—Italy).

After the pressing step 20 the concrete layer 7 is substantially formed, except for further submitting it to a drying and/or curing operation in the thermal chamber 13 having a controlled temperature and humidity and a hot-air operation, for example. In the thermal chamber 13 the humidity must be further removed or is supplied if a substantially dry process has been carried out.

The residence time in the thermal chamber depends on the features of the concrete layer inserted therein. Just as an indication, it is of about twelve hours on an average.

At this point of the process or also in a preceding step, application of the upper layer 14 prepared in an independent manner, occurs.

The upper layer 14, if applied at this point of the process, is glued to and pressed against the concrete layer 7.

If applied in a previous time, the upper layer 14 can be placed on the concrete layer 7 being formed before the latter is submitted to the pressing step 20 and it is this pressing step that performs the function of permanently engaging the layers with each other. In this case the two layers are both and jointly sent to the thermal chamber 13.

After a steady union of layers 7 and 14 and completion of same, panel 1 is sent to a final grinding step 21 at which it is perfectly trimmed at the side edges 1 b.

A further finishing step of the face in sight 1 a is also possible.

The invention achieves important advantages.

In fact a panel 1 has been manufactured which is provided of high functional and mechanical features, surprisingly given by a concrete layer.

In fact once finished, the concrete layer appears to be very solid and reliable: it has a density of at least one thousand and seven hundred kilos per cubic meter and a resistance to a concentrate load of at least ten Kn.

The panel is then advantageous because it appears to be provided with the greatest dimensional stability, due to its concrete structure. Therefore it does not show important expansions and shrinkages bound to the environmental temperature and does not require peripheral protections.

In addition it has a great dimensional precision both due to said grinding step and to the fact that inaccuracies in mounting to not exist, since the concrete layer and upper layer are joined together.

Further important advantages are connected with the fact that there are no elements contributing to fire and therefore it is greatly fire-proof.

It also has a complete absence of water absorption and therefore a maximum waterproofness is ensured.

The panel is then relatively light-in-weight and above all it is simple and inexpensive and can be widely used.

The invention is susceptible of variations falling within the inventive idea. For example, the part in view of panel 1 can be of any structure and the shape or finishing of this structure can be variously arranged to obtain decorative patterns or effects. The decorative effects are obtainable for example by elements made by molding and possibly superposed on the upper layer 14 or combined therewith. In addition panel 1 is also usable out of the raised flooring field, as a coating for outer or inner walls for example, or to make architectonic structures, as it is in any case useful and advantageous due to its functional and mechanical features and to its low cost. 

1. A panel in particular for raised flooring, of the type comprising at least one concrete layer (7) having at least cement (8), inert material (9), and additives (10 a, 10 b) as its components, said panel comprising a micro-reinforcement made of fibers (11) resisting to tensile stresses, and said inert material (9) consisting of granules having diversified sizes to limit the presence of gaps between said granules and to reduce the porosity of said concrete layer (7).
 2. A panel as claimed in claim 1, wherein said fibers (11) are a glass yarn of the alkaline-resistant (AR) type.
 3. A panel as claimed in claim 1, wherein said fibers (11) are a compound including glass yarns of the alkaline-resistant (AR) type and synthetic fibers of plastic material.
 4. A panel as claimed in claim 1, wherein said fibers (11) are in an amount of at least two percent of the weight of said concrete layer.
 5. A panel as claimed in claim 1, wherein said inert material (9) comprises a big aggregate (9 a), a medium aggregate (9 b) having smaller sizes than those of said big aggregate (9 a) and substantially defined by sand, and a thin aggregate (9 c) having smaller sizes than those of said medium aggregate (9 b) and in an amount by weight similar to or greater than that of said medium aggregate (9 b).
 6. A panel as claimed in claim 5, wherein said big aggregate (9 a) includes granules having sizes included between ten and two millimeters, said medium aggregate (9 b) includes granules having sizes included between one millimeter and half a millimeter, and said thin aggregate (9 c) includes granules having sizes included between five hundredths and one hundredth of a millimeter.
 7. A panel as claimed in claim 5, wherein, with respect to the weight of said concrete layer (7), said big aggregate (9 a) is in an amount substantially included between twenty and thirty-five percent, said medium aggregate (9 b) is in an amount substantially included between ten and twenty percent, and said thin aggregate (9 c) is in an amount substantially included between fifteen and twenty-five percent.
 8. A panel as claimed in claim 6, wherein in said concrete layer (7) a grit (11 a) is provided, said grit (11 a) being made of granules of glass of the alkaline-resistant type (AR) having smaller sizes than those of said medium aggregate (9 b).
 9. A panel as claimed in claim 8, wherein said grit (11 a) includes granules having a size substantially included between two tenths and four tenths of a millimeter.
 10. A panel as claimed in claim 1, wherein said components of said concrete layer (7) are under compacting conditions as determined by pressures of at least five hundred metric tons per square meter.
 11. A panel as claimed in claim 1, comprising an upper layer (14) of a material selected at least from ceramic grés, antacid resins, PVC, wood, and ecological coating including titanium oxide TiO₂, said upper layer (14) defining a face in sight (1 a) of said panel (1).
 12. A panel as claimed in claim 11, wherein said upper layer (14) is integral with said concrete layer (7) by gluing and pressing, to define a single manufactured article with said concrete layer (7).
 13. A panel as claimed in claim 11, wherein said upper layer (14) and concrete layer (7) jointly define side edges (1 b) transverse to said face in sight (1 a) and ground.
 14. A process for manufacturing a panel in particular for raised flooring, of the type comprising at least one concrete layer (7) having at least cement (8), inert material (9), and additives (10 a, 10 b) as its components, said inert material (9) being selected from granules having diversified sizes to limit the presence of gaps between said granules, and said components being bound to each other through a micro-reinforcement made of fibers (11) resisting to tensile stresses, and being compacted with each other at high pressure through a pressing step (20) to reduce porosity of said concrete layer (7).
 15. A process as claimed in claim 14, wherein in said pressing step (20) said components are submitted to pressures of at least 500 metric tons per square meter, in a mould (12).
 16. A process as claimed in claim 14, wherein said pressing step (20) is performed in combination with a vibration of said mould (12).
 17. A process as claimed in claim 14, wherein said inert material (9) is selected from at least three sizes differentiated from each other and in amounts by weight similar to each other, a medium aggregate being substantially defined by sand.
 18. A process as claimed in claim 14, wherein said concrete layer (7) is engaged in an irremovable manner with an upper layer (14) by gluing and mutual pressing.
 19. A process as claimed in claim 18, wherein said concrete layer (7) and upper layer (14) are jointly submitted to a grinding step (21) to define their size features. 